Feed mechanism for a drilling machine

ABSTRACT

A drilling machine for tapping a pipe includes a rotatable boring bar which is advanced linearly by a ball bearing nut and screw combination, the nut being fixed to the boring bar and the screw being rotated by a power source. The power source is inactivated when the pipe has been tapped, and the fluid pressure in the main will act on the boring bar tending to force it in a reverse direction thereby tending to rotate the screw rapidly in an uncontrolled manner. To prevent this the machine includes a friction brake of special design which automatically restrains reverse rotation of the screw yet is not sufficient to prevent manual reverse rotation of the screw by the operator.

United States Patent Inventors Frank H. Mueller;

John J. Smith; Lynn D. Edwards, all of FEED MECHANISM FOR A DRILLINGMACHINE 4 Claims, 2 Drawing Figs.

US. Cl

Int. Cl ..Fl6d 19/00, Fl6h 1/18, B23b 41/08 Field ofSearch 74/8915,

424.8 B, 424.8 R; 192/93 R, 93 B; 77/42 [56] References Cited UNITEDSTATES PATENTS 2,986,959 6/1961 Van Scoy 4. 77/42 3,293,952 12/1966Fairbanks 77/42 Primary ExaminerLeonard H. Gerin AtmrneyCushman, Darbyand Cushman ABSTRACT: A drilling machine for tapping a pipe includes arotatable boring bar which is advanced linearly by a ball bear ing nutand screw combination, the nut being fixed to the boring bar and thescrew being rotated by a power source. The power source is inactivatedwhen the pipe has been tapped, and the fluid pressure in the main willact on the boring bar tending to force it in a reverse direction therebytending to rotate the screw rapidly in an uncontrolled manner To preventthis the machine includes a friction brake of special design whichautomatically restrains reverse rotation of the screw yet is notsufficient to prevent manual reverse rotation of the screw by theoperator.

FEED MECHANISM FOR A DRILLING MACHINE REFERENCE TO RELATED APPLICATIONThis application is a division of application Ser. No. 760,006, filedSept. 16, 1968 now Patent No. 3,541,894.

DESCRIPTION OF THE INVENTION This invention relates to machines fordrilling or tapping high-pressure mains and pipes and more particularlyit relates to improvements in a drilling machine of the type whichincludes a rotatable boring bar and a feed mechanism for advancing orretracting the bar independently of rotation of the latter.

In its broad form the invention defines an improvement in the type ofdrilling machine in which the linear feed mechanism comprises a nut andscrew combination wherein rotation of one of the members produces linearmovement of the other member, this movement being transmitted to theboring bar through any suitable connection. The feed mechanism can beoperated by hand, or it can be operated with an automatic drive whichadvances the boring bar, as it rotates, at a rate appropriate for acutting operation. When the main or pipe has been cut by a tool carriedat the outer end of the boring bar, the feed mechanism of the type ofmachine under consideration is inactivated, as by a clutch operativelyconnected between the drive motor and the feed screw. At this time thetool and the adjacent end of the boring bar will be subjected to hefluid pressure in the pipe which has been pierced, and this pressuretends to push the boring bar in the opposite, or retract direction.However, actual movement of the bar is prevented by the interaction ofthe threaded connection which forms part of the feed mechanism.

According to the broad principles of the present invention a ballbearing nut and screw combination is substituted for the moreconventional Acme threaded nut and screw in a feed mechanism of thistype in order to render the feed and retract action faster and smoother,and at the same time an automatic one-way brake is provided to preventline pressure from forcing the boring bar in a retract direction at theend of a cut. It will be appreciated that the very low friction in aball bearing connection between the nut and the screw is insufficient toprevent the boring bar from overhauling very rapidly, when subjected toline pressure. It follows that simple substitution of a ball bearingunit for an Acme thread or the like would permit the feed mechanism todamage itself unless some provision is made for resisting retraction ofthe boring bar at a time when it is subject to line pressure. Theone-way brake provided by the present invention exerts a frictional dragon the rotating element of the feed mechanism at the appropriate timewhich is just sufficient to prevent back running of the bar, yet whichis not sufficient to prevent easy manual rotation of the element toeffect controlled retraction of the bar. Preferably the braking force isautomatically applied in proportion to the line pressure on the bar.

It is a more specific object of the invention to provide a oneway brakein a drilling machine of the type disclosed in Mueller patents 2,833,167and 2,925,160. In this kind of machine the automatic drive for the feedmechanism includes a countershaft and differential gearing and a clutchwhich transmit rotary motion from a motor driven element to the feedscrew. The countershaft and the feed screw shaft are permanently gearedtogether, and the boring bar is fixed to the nut which threadedlyengages the feed screw. The clutch automatically disengages at the endof a cutting operation, with the result that the aforementionedretraction force on the boring bar due to line pressure is transmittedto the nut-screw connection and would cause the feed screw to runbackwards out of control if the nut-screw unit is of the ball bearingtype.

The one-way brake of the present invention, as it pertains to this kindof drive mechanism, includes a differential gear arrangement between thecounter shaft and the shaft of the feed which resides between the hubsof two of the gears and acts as a friction brake. In the preferredconstruction a gear is carried on the countershaft, which is parallel tothe feed screw, the gear being automatically connectable to thecountershaft by a suitable one-way clutch arranged such that the gearrotates freely on the countershaft when the boring bar is being advancedand becomes fixed to the countershaft when the boring bar retracts. Anidler gear is freely rotatable on the feed screw shaft and is incontinuous mesh with the clutched gear wheel. A thrust washer or thelike is carried on the feed screw shaft between the hub of the idlergear and the hub of another gear, the latter being fixed to the shaftand in meshing engagement with a gear fixed to the countershaft. Thelatter two gears are part of the drive mechanism as disclosed in theaforesaid patents and define a continuous positive drive connectionbetween he countershaft and the feed screw shaft.

When the countershaft begins to rotate due to the aforementioned forceof line pressure on the boring bar, the clutched gear becomes locked tothe countershaft and begins to rotate the idler gear. A differentialefiect is built into the gears so that the idler gear tends to rotate ata slower speed than the feed screw shaft. The result is that the thrustwasher exerts a frictional force on the drive gear which is justsufficient to prevent back running of the feed screw. The clamping loadon the thrust washer is proportional to the line pressure so that thebraking force is self-adjusting.

The invention will be further understood from the following detaileddescription of an illustrative embodiment taken with the drawings inwhich:

FIG. 1 is a fragmentary longitudinal sectional view of a drillingmachine embodying this invention; and

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1.

Referring to FIG. 1, there is shown a portion of a drilling machine inwhich many of the parts and their cooperation with each other aresubstantially the same as disclosed in the aforesaid patents 2,833,167and 2,925,160. The major differences lie in the provision of a ballbearing connection in the feed mechanism for advancing and retractingthe boring bar of the machine and in the provision of gears 302 and 304,a thrust washer 306 and various associated parts, all of which will bedescribed in detail hereinafter in conjunction with a generaldescription of the remainder of the machine. At the outset it issufficient merely to explain that the thrust washer will function asautomatic friction brake under certain conditions to prevent driving ofthe boring bar in a retract direction by the force of line pressure.

The drilling machine includes a barrel 10 provided at one end thereofwith a platelike eccentric circumferential flange 12, which, inconjunction with a bowllike top cap 14 bolted thereto, constitutes agear housing 16. At its other end (not shown) the barrel 10 has securedthereto a driving gear housing (not shown) adapted to be detachablysecured to one end of a valve (not shown) through which the boring bar18 of the machine is adapted to extend for main cutting or drillingoperations, all as described more in detail in the aforementionedpatent.

Journaled in a bushing 20 in the barrel 10 is the corresponding end of adrive tube 22 which projects into the housing 16 and has a pair of gearssecured thereon by a key 28. The other end (not shown) of the tube 22projects into and is driven from within the aforementioned driving gearhousing. Received in the drive tube 22 is the hollow boring bar '18, theupper portion of which has a close sliding fit in the drive tube and issplined thereto for rotation thereby an axial movement relative thereto,preferably by a pair of keys (not shown) secured to the bar and slidablein diametrically opposite interior longitudinal grooves or keyways (notshown) extending the length of the drive tube 22. The upper interiorportion of the boring bar 18 is enlarged to provide a shoulder 30 whichsupports an inwardly overhanging abutment ring 32 against which isseated a ball bearing nut unit which includes a conventional ballbearing nut 308, such as one having a three-lead thread, and a tubularretainer 310 fixed to the nut 308. The retainer 310 is fixed againstrotation relative to the boring bar 18 by keys 36, and fixed againstrotation relative to the raceway element 308 by keys 312. The entireunit is fixed against axial movement relative to the bar 18 by aretaining ring 38 threaded into the upper end of the bar 18 and lockedin place by set screws 40 bearing against the right-hand end of theretainer 310.

A hollow feed screw 42 is engaged within thenut 308 and extendscoaxially within the boring bar 18. The right-hand end of the screw 42has an enlarged, unthreaded extension 44 which extends through the uppergear housing 16 and projects through and is journaled in a sleevebearing 46 supported by the top cap 14. The projecting outer end of thescrew extension 44 terminates in a squared or otherwise noncircularlyformed outer end 48 for detachable engagement within the complementarysocket of a crank handle 50, only a portion of which is shown. Withinthe gear housing 16 the screw extension 44 has a gear 52 keyed theretoat 53. The feed nut 308 and the feed screw 42 constitute the feedmechanism of the machine for advancing the boring bar 18 on relativerotation between the nut 308 and the screw 42.

An axially-shiftable countershaft 54 is journaled in a cap bearing 56mounted in the flange 12 and in a sleeve bearing 58 mounted in the cap14, in laterally spaced parallel relation to the feed screw 42. At oneend the countershaft 54 projects out of the housing 16 and has anoperating knob 60 pinned thereto. The end 61 is squared to receive thecrank handle 50, the latter being removable from the end 48. Mounted onthe countershaft 54 is a gear 62 that is selectively connectable anddisconnectable with the countershaft for rotation therewith or relativethereto by means of a dive-key type of clutch mechanism. This clutchmechanism includes a spring key 64 received with sliding clearance in alongitudinally extending slot 66 in the countershaft 54. The base orfoot portion 68 of the key is secured in the slot by a transverse pin70, while the head 72 of the key is urged by its spring shank 74 toproject out of the slot 66 for engagement within a longitudinal groove76 in the interior of the hub of the gear 62. The key 64 is engaged anddisengaged with the gear 62 by axial movement of the countershaft 54,which may be shifted manually by the knob 60. Thus, when thecountershaft 54 is in the axial position shown in FIG. 1, the key 64projects into the groove 76 in the gear 62 so as to lock the latter tothe countershaft for rotation therewith. When the countershaft 54 isshifted to the left, however, an angular face on the key 64 bearsagainst the edge of an aperture in a bushing 80 on the shaft 54 and camsthe key head 72 back into the clot 66 and out of engagement with thegear 62 so that the latter can rotate relative to the countershaft.

Also mounted on the countershaft 54, by a key 82, is a gear 84. Thegears 24 and 62 are in constant mesh while the gears 52 and 84 are inconstant mesh. Consequently, when the clutch mechanism is engaged, thegears 24 and 62, the countershaft 54, and the gears 82 and 52 form apower train that constitutes an automatic drive for the feed mechanism.The ratios of the gears in the automatic drive are such that when theclutch mechanism is engaged, rotation of the drive tube 22 drives thefeed screw 42 at a slightly greater rate of rotation than the feed nut308 to thereby advance the boring bar 18 at an appropriate rate forcutting a main. When the aforedescribed clutch mechanism is disengaged,manual rotation of the feed screw 42, by the crank handle 50, when thedrive tube 22 and the nut 308 are at rest, rotates the feed screw 42 ata rate fast enough to rather rapidly thread the nut therealong for afast advance or retraction of the boring bar 18.

The machine also embodies a preset feed mechanism which can be adjustedso that when the machine is in automatic feed and the boring bar 18advances a predetermined distance from any axial position of such bar,the automatic drive will be disengaged and stop further advance of theboring bar. For this purpose, the preset feed mechanism includes meansfor shifting the countershaft 54 from its automatic feed to its handfeed position, i.e., from its clutch-engaged to its clutch-disengagedposition. This shifting means includes a cam sleeve 86, shown formed intwo parts welded together for manufacturing convenience, which isjournaled on the countershaft 54. One end of the sleeve 86 is formedwith what may be termed a counterbore that forms a shoulder 88 providedwith diametrically opposite, V-shaped cam grooves 90 within which ridethe opposite ends of a pin or cam follower 92, extending diametricallythrough the countershaft 54, when the latter is in its automatic feedposition.

it will be seen that if the cam sleeve 86 is restrained against rotationand the countershaft 54 continues to rotate, the projecting ends of thecam pin 92 will ride up the inclined sidewalls or surfaces of the camgrooves 90 and force the countershaft 54 to shift to the left from itsautomatic feed to its hand feed position. In such latter position of thecountershaft 54, the projecting ends of the cam pin 92 clear theshoulder 88 in the cam sleeve 86 so that the countershaft can rotatefreely relative to the cam sleeve and enable operation of the manualfeed.

The countershaft 54 is yieldably retained in its automatic feed positionby a detent 94 slidable in a radial interior blind socket 96 in the camsleeve 86 and urged inwardly by a spring 98 interposed between thedetent and the base of the socket. It will be noted that the sleeve 86is provided with a radial bore 100 aligned with the socket 96 so thatthe spring 98 and detent 94 can be passed through the bore 100 and intothe socket in assembling the detent elements with the cam sleeve. Thedetent 94 has a rounded nose engageable within one or the other of apair of diametrically opposite circular recesses 102 and 103 in thecountershaft 54.

When the detent 94 is engaged with one of the recesses 102, 103 in thecountershaft 54, not only is the latter yieldably retained in itsautomatic feed position, but also the projecting ends of the pin 92 areyieldably maintained out of engagement with the sides of the cam grooves90, as shown in FIG. 1. Consequently, when the cam sleeve 86 is rotatingwith the shaft 54, no camming action between the pin 92 and the sides ofthe cam grooves 90 can occur because of hammering action therebetweenoccasioned by vibratory conditions, because of the out-of-engagementrelationship between these parts yieldably maintained by the detent 94and one of its corresponding recesses 102, 103 in the countershaft 54.

The mechanism for arresting rotation of the cam sleeve 86 constitutes apart of the aforementioned preset feed mechanism that is driven by thegear 26 and which is settable by a rotatable and axially shiftable shaft104 one end of which projects out of the housing 16 and has a knurledoperating knob 106 secured thereon. The details of the preset feedmechanism are described in the aforementioned patents and form no partof the present invention. It is sufficient for the purposes here topoint out that the preset feed mechanism includes an arm 108 having anaperture therein rotatably receiving a portion of the cam sleeve 86, andwhich arm is automati cally movable by operation of the preset feedmechanism to the left from the position shown in FIG. 1. A counterboreat one end of the aperture in the arm 108 is provided with a radial stoplug engageable with a radial lug 112 on and adjacent one end of the camsleeve 86, when the arm 108 is shifted to the left automatically by thepreset feed mechanism, to arrest or prevent rotation of the cam sleeve.

As previously described, such arrestment will automatically shift thecountershaft 54 from automatic to hand feed position.

Referring again to the one-way brake arrangement which forms animportant part of the present invention it is explained that the gear302 is provided with a one-way clutch arrangement such that it is lockedto the countershaft 54 when the latter rotates in a directioncorresponding to retraction of the boring bar 18 and is otherwise freelyrotatable relative to the countershaft 54. To this end the gear 302 isprovided with a keyway 314 and a key 316, the latter having a projection318 which is loosely retained in a socket 320 in the gear. A spring 322urges the key 316 downwardly so that it rides on the surface of thecountershaft 54 when the latter is in the automatic drive position shownin FIG. 1.

When the countershaft 54 s shifted to the left by the feed settingmechanism or by hand, the key 316 is urged by the spring 322 into agroove 324 in the countershaft 54. As seen in FIG. 2 one wall 326 of thegroove 324 is generally radial so that the key 316 will lock againstthis wall when the countershaft 54 turns clockwise. The other wall 328is inclined so that the key 316 will slide over it, ratchetlike, whenthe countershaft 54 turns counterclockwise. When the eountershaft 54 isshifted again to the right, the key 316 is cammed upwardly against theaction of the spring 322 by engagement of the arcuate end 330 of the key316 with the edge of the keyway 324.

The gear 304 is an idler gear which is freely rotatable on the shaftextension of the feed screw 42 and which engages a thrust bearing 120interposed between the gear 304 and a fixed thrust collar 122. Thethrust washer 306 is also freely rotatable on the shaft extension and isin contact with the hub portions of the idler gear 304 and the gear 52.When the countershaft 54 is in the right-hand position, as shown, thegears 304 and 52 and the thrust washer turn as a unit, because the gear302 turns freely on the countershaft 54. However, when the key 316enters the keyway 324 due to movement of the countershaft 54 to theleft, the gear 302 becomes a driven gear upon rotation of thecountershaft 54 in a direction corresponding to retraction of the boringbar 18. The gears 52, 84, 302, and 304 are constructed with adifferential effect such that the idler gear, when driven, turns at aslower rate than the gear 52. The thrust washer 306 therefore acts as afriction brake against the gears 52 and 30 1 when the boring bar 18retracts or tends to retract.

Referring more specifically to the operation of the machine just priorto operation of the brake arrangement it will be recalled that thecountershaft 54 is automatically shifted to the left when the boring bar18 has advanced to the position previously set by an operator on thefeed set mechanism (not shown). The shifting movement occurs as a resultof the arresting of rotation of the cam sleeve 86 and consequentengagement of the pin 92 with the cam grooves 90. As previouslydescribed, the set mechanism (not shown) arrests rotation of the camsleeve 86 by moving the arm 108 into engagement with the lug 112 on thecam sleeve 86. Shifting of the countershaft 54 to the left disconnectsthe rotative drive between the power driven drive tube 22 and thecountershaft 54 by camming the spring key 64 out of engagement with thegear 62. The key 82 between the gear 84 and the countershaft 54 permitsthe latter to move axially with respect to the gear 84, so that thegears 84 and 52 remain in meshing engagement. Shifting of thecountershaft 54 to the left also brings into operation the one-wayclutch arrangement between the countershaft 54 and the gear 302.

Once the rotative drive between the drive tube 22 and the countershaft54 becomes disconnected, as just described, the feed screw 42 issubjected to a rotative force in the opposite, or retract direction dueto the pressure of the fluid in the perforated pipe or main acting onthe boring bar and being converted to torque by the ball bearing nut308. The torque may be quite high, inasmuch as the pressure in the linemay exceed 1000 pounds per square inch. This torque is transmitted fromthe feed screw extension to the countershaft 54 by the gears 52 and 84,and then to the idler gear 304 by means of the clutched gear 302. Thedifferential action of the gears 52, 84, 302 and 304 tends to rotate thegear 304 more slowly than the gear 52 so that frictional forces aregenerated between the faces of the thrust washer 306 and the hubs of thegears 304 and 52.

The frictional forces are proportional to the fluid pressure acting onthe boring bar 13 due to the tendency of the feed screw to move to theright and to thereby clamp the washer 306 between the gears 30 i and 52.The design is such that the friction is slightly more than sufficient toprevent rotation of the feed screw 42 by the line pressure alone yet islow enough to be easily overcome by manual rotation of either thecountershaft 54 or the feed screw extension in a retract direction. Inthis regard it will be understood that the braking action will depend inlarge part on the diameter and material of the washer 306, on the speeddifferential effect of the gears and on the tightness of the gearsagainst the washer and that many variations in these parts may beemployed to obtain the desired results.

It will be appreciated that the one-way brake arrangement will functionalso in the event that, for some reason, it is necessary to stop thedrilling operation and withdraw the boring bar 13 before the cuttingoperation has been completed, as when a pilot drill breaks. In thiscase, the countershaft 54 is first shifted manually to the left bypushing on the knob 60, and the braking action of the thrust washer 306occurs in fluid manner described above. Then, when it is desired toadvance the boring bar 18 against line pressure, the hand crank 50 willbe placed over the end 61 of the countershaft 54 and turned in theappropriate direction so as to take advantage of the gear reductionbetween the gears 84 and 52. Under these conditions the gear 302 isdeclutched from the countershaft 54, and the gears 52 and 304 turntogether on the bearing 120, removing the frictional load of the brake.

When initially installing the machine on a pipe, the boring bar 18 canbe advanced rapidly to its desired position by using the hand crank 50on the end 48 of the feed screw extension.

There is no pressure load on the boring bar 18 at this time, and rapidmanual advance is obtained due to the ease with which the feed screw 42may be turned in the ball bearing nut 308. The brake is, of course,inoperative due to declutching of the gear 302 from the countershaft 54.

While preferred embodiments of the present invention have beendescribed, further modifications may be made without departing from thescope of the invention. Therefore, it is to be understood that thedetails set forth or shown in the drawings are to be interpreted in anillustrative, and not in a limiting sense, except as they appear in theappended claims.

ll. A power train comprising: a translatable element; a rotary element;a drive connection between said elements operable to convert rotarymotion of said rotary element to linear movement of said translatableelement and operable to convert linear movement of said translatableelement to rotary motion of said rotary element; a drive connectionoperatively connected with said rotary element for imparting rotarymotion thereto in one direction from a rotary power source to urge saidtranslatable element in one direction, said drive connection includingengageable and disengageable clutch means for rendering said connectionoperative and inoperative, engageable and disengageable brake meansoperative when said clutch means is disengaged to apply to restrainingforce to said rotary element to resist yet not prevent rotation thereofin a direction reverse to said one direction thereby preventing uncontrolled reverse rotation of said rotary element as a result ofexternal linear forces applied to said translatable element in saidreverse direction when said clutch means is disengaged.

2. A drive train as in claim 1 wherein said brake means includes afriction element having a surface facing in said one direction andengaging an oppositely facing surface on a part fixedly carried by saidrotary element whereby the friction between said surfaces isproportional to said external linear forces applied to said translatableelement.

3. A drive train as in claim 2 wherein said friction element is freelymounted on said rotary element for rotation relative thereto and whereinsaid brake means further includes a hub member freely mounted on saidrotary element for rotation relative thereto, said hub member engagingthe surface of said friction element opposite said first-mentionedsurface, and drive means operatively connected with said rotary elementand with said hub member for rotating the latter in a different modefrom said rotary element when the latter turns in said reverse directionto thereby create frictional forces against said part which is fixedlycarried by said rotary element.

tershaft, a gear connection including a one-way clutch between saidcountershaft and said hub member and operable to rotate the latter onlywhen said rotary member turns in said reverse direction.

1. A power train comprising: a translatable element; a rotary element; adrive connection between said elements operable to convert rotary motionof said rotary element to linear movement of said translatable elementand operable to convert linear movement of said translatable element torotary motion of said rotary element; a drive connection operativelyconnected with said rotary element for imparting rotary motion theretoin one direction from a rotary power source to urge said translatableelement in one direction, said drive connection including engageable anddisengageable clutch means for rendering said connection operative andinoperative, engageable and disengageable brake means operative whensaid clutch means is disengaged to apply to restraining force to saidrotary element to resist yet not prevent rotation thereof in a directionreverse to said one direction thereby preventing uncontrolled reverserotation of said rotary element as a result of external linear forcesapplied to said translatable element in said reverse direction when saidclutch means is disengaged.
 2. A drive train as in claim 1 wherein saidbrake means includes a friction element having a surface facing in saidone direction and engaging an oppositely facing surface on a partfixedly carried by said rotary element whereby the friction between saidsurfaces is proportional to said external linear forces applied to saidtranslatable element.
 3. A drive train as in claim 2 wherein saidfriction element is freely mounted on said rotary element for rotationrelative thereto and wherein said brake means further includes a hubmember freely mounted on said rotary element for rotation relativethereto, said hub member engaging the surface of said friction elementopposite said first-mentioned surface, and drive means operativelyconnected with said rotary element and with said hub member for rotatingthe latter in a different mode from said rotary element when the latterturns in said reverse direction to thereby create frictional forcesagainst said part which is fixedly carried by said rotary element.
 4. Adrive train as in claim 3 wherein said drive means for rotating said hubmember includes a countershaft disposed parallel to said rotary element,a continuously engaged gear connection between said rotary element andsaid countershaft, a gear connection including a one-way clutch betweensaid countershaft and said hub member and operable to rotate the latteronly when said rotary member turns in said reverse direction.